An image processing apparatus includes a memory unit which stores data of a first projection image and data of a second projection image, which are associated with the same object and are captured in different imaging directions, a display unit which displays the data of the first projection image and the data of the second projection image, a designation operation unit which is configured to designate a plurality of points on the displayed first and second projection images, and an operation supporting unit which generates operation supporting information for supporting an operation of designating, by the designation operation unit, the plurality of points on the second image, which anatomically correspond to the plurality of points designated on the first projection image.
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5. An image processing method comprising:
extracting a center axis of a target blood vessel using data of a 3d image of the target blood vessel and calculating tangent vectors with respect to multiple points on the center axis;
calculating angles of the tangent vectors to a projection plane which is orthogonal to said center axis;
generating a color map as a projection image representing a direction of running of the target blood vessel by projecting volume data using the same view point, view angle and projection plane as those used in generating a projection image representing a blood vessel configuration, including assigning a color value, which corresponds to the calculated angle, to each of the multiple points; and
displaying the color map.
1. An image processing apparatus comprising:
a memory unit which stores data of a 3d image relating to a target blood vessel within a subject;
a vector calculation unit which extracts a center axis of the target blood vessel using the data of the 3d image and calculates tangent vectors with respect to multiple points on the center axis;
an angle calculation unit which calculates angles of the tangent vectors to a projection plane which is orthogonal to said center axis;
a map generation unit which generates a color map as a projection image representing a direction of running of the target blood vessel by projecting volume data using the same view point, view angle and projection plane as those used in generating a projection image representing a blood vessel configuration;
a display unit which displays the color map; and
wherein the map generation unit assigns a color value, which corresponds to the calculated angle, to each of the multiple points.
2. The image processing apparatus according to
3. The image processing apparatus according to
4. The image processing apparatus according to
a generation unit which generates data of a 2D image of the target blood vessel by projection onto the projection plane, using the data of the 3d image; and
a combining unit which combines the data of the 3d image of the target blood vessel and the map data.
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This application is a division of and claims the benefit of priority under 35 U.S.C. §120 from U.S. Ser. No. 11/364,194 filed Mar. 1, 2006, and claims the benefit of priority under 35 U.S.C. §119 from Japanese Patent Applications Nos. 2005-061600 filed Mar. 4, 2005; and No. 2005-061601 filed Mar. 4, 2005, the entire contents of each of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image processing apparatus having a function of reconstructing a three-dimensional (3D) image from projection images that are captured from two directions, or a function of generating projection image data from volume data relating to a configuration of a fine tubular object such as a blood vessel within a subject.
2. Description of the Related Art
There is known a technique of reconstructing a 3D image from projection images captured from two directions in order to visualize a running of, typically, a blood vessel, as shown in
If the operator designates a point (characteristic point) A on the lateral image as an anatomically characteristic part and designates a point (corresponding point), which is associated with same part as the characteristic point A, on the line C on the frontal image, the position of the characteristic part on the line B can be specified. In short, in order to specify a 3D position, it is necessary to designate corresponding points on two-directional images in association with the same part.
Thus, the operator is required to perform a work to designate corresponding points on two-directional images by means of a pointer such as a mouse. By increasing the number of corresponding points, the precision of the 3D image is enhanced. When a 3D image of blood vessels, which branch in a complex fashion, is to be acquired, many corresponding points need to be designated.
Typical examples of the method of designating such corresponding points are shown in
Practically, it is very time-consuming to designate several-ten, in some cases, several-hundred corresponding points. In either of the above-described two methods, errors tend to occur in establishing the correspondency of the corresponding points.
There have been an increasing number of opportunities in which configurations of fine tubular objects, typically, blood vessels are displayed three-dimensionally. Practically, a projection image (re-projection image) is generated from 3D image data having depth information relating to blood vessels, and shading is added to the image to achieve three-dimensional visualization.
In fact, however, it is very difficult to understand the direction of running of blood vessels in the direction of image projection.
An object of the present invention is to reduce the load of a work of designating corresponding points, which are associated with a common part, on projection images captured in two directions, this work being needed when a 3D image is reconstructed from the projection images captured in two directions, and to provide an operation support to avoid erroneous designation of such corresponding points.
Another object of the invention is to provide an image processing apparatus and an image processing method for displaying a projection image relating to an object of a fine tubular shape, such as a blood vessel, along with information of the direction of running of the object.
According to a first aspect of the present invention, there is provided an image processing apparatus comprising: a memory unit which stores data of a first projection image and data of a second projection image, which are associated with the same object and are captured in different imaging directions; a display unit which displays the data of the first projection image and the data of the second projection image; a designation operation unit which is configured to designate a plurality of points on the displayed first and second projection images; and an operation supporting unit which generates operation supporting information for supporting an operation of designating, by the designation operation unit, the plurality of points on the second image, which anatomically correspond to the plurality of points designated on the first projection image.
According to a second aspect of the present invention, there is provided an image processing apparatus comprising: a memory unit which stores data of a plurality of projection images, which are associated with the same object and are captured in different imaging directions; a display unit which displays the data of the plurality of projection images; a designation operation unit which is configured to designate a plurality of points on the displayed projection images; and an operation supporting unit which generates operation supporting information for supporting an operation of designating, by the designation operation unit, a point on one of the plurality of projection images, which anatomically corresponds to at least one of points designated on another projection image of the plurality of projection images.
According to a third aspect of the present invention, there is provided an image processing apparatus comprising: a memory unit which stores data of a 3D image relating to a fine tubular object within a subject; a tangent vector calculation unit which calculates a tangent vector of the object with respect to multiple points on the object, using the data of the 3D image; an angle calculation unit which calculates an angle of the tangent vector to a projection plane; a map generation unit which generates map data of the object by assigning a display mode, which corresponds to the calculated angle, to each of the multiple points; and a display unit which displays the map data.
According to a fourth aspect of the present invention, there is provided an image processing method comprising: calculating a tangent vector of an object with respect to multiple points on the object, using data of a 3D image relating to a fine tubular object within a subject; calculating an angle of the tangent vector to a projection plane which is arbitrarily set; generating map data of the object by assigning a display mode, which corresponds to the angle, to each of the multiple points; and displaying the map data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.
An image processing apparatus according to a first embodiment of the present invention (image processing apparatus) will now be described with reference to the accompanying drawings. In this embodiment, the image processing apparatus is described as being built in a biplane X-ray imaging apparatus. Needless to say, the image processing apparatus may be constructed as a single unit. In addition, this embodiment may be constructed as a program for causing a computer to execute a 3D image reconstruction process. A computer-readable memory medium that stores the program may also be provided.
The image processing apparatus of this embodiment is an apparatus having a function of reconstructing a 3D image from projection images captured in two directions (two-directional images). The kind or type of projection images is not limited. It is possible to use either two-directional images which are captured by a single-plane X-ray imaging apparatus, or two-directional images which are captured by a biplane X-ray imaging apparatus. In this example, general biplane X-ray imaging is employed.
The biplane X-ray imaging apparatus, which is equipped with the image processing apparatus of the present embodiment, includes a frame control unit 111. The frame control unit 111 arbitrarily controls the positions and directions of the C-arm 13 and Ω-arm 23 in accordance with the operator's instruction that is input from an operation table 123 connected to the frame control unit 111 via an interface 121, and the frame control unit 111 acquires data relating to the imaging positions and imaging directions of the respective imaging systems from sensors (not shown). An image memory unit 117 stores the data relating to the imaging positions and imaging directions of the respective imaging systems, together with projection image data which is generated from the X-ray detectors 114-1 and 114-2 via a detector control unit 115 in sync with X-rays that are generated from the X-ray tubes 112-1 and 112-2 by application of tube voltage from an X-ray control unit 113. A display unit 127 is a display device such as a CRT, and is connected via an image display control unit 125. A blood vessel extraction unit 119 extracts an image of a blood vessel, which is formed of the projection image data by, e.g. a threshold process. A 3D image reconstruction operation supporting unit 129 is provided in order to support the operator's operation which is necessary for reconstructing a 3D image. Typically, when a corresponding point is designated on one of the projection images, the 3D image reconstruction operation supporting unit 129 outputs, as supporting information, information for specifying an already designated corresponding point on the other projection image, which is associated with the corresponding point that is to be designated on the one of the projection images. The operation support by the 3D image reconstruction operation supporting unit 129 will be described later in greater detail. A 3D image reconstruction unit 131 reconstructs 3D image data of the blood vessel image that is extracted from the projection images by the blood vessel extraction unit 119, on the basis of the positional relationship between a plurality of corresponding points designated by the operator under the operation support by the 3D image reconstruction operation supporting unit 129.
In the description below, 3D image data include the following two types (A) and (B).
3D image data of type (A) is mainly generated by a CT or an MRI. Even in an X-ray diagnosis apparatus, volume-reconstructed data corresponds to the 3D image data of type (A). 3D image data of type (A) have values with respect to all voxels within a 3D region. Specifically, with respect to a 3D region of, e.g. 512×512×512, 134, 217, 728 values are given.
3D image data of type (B) is given as a vector amount (vector data) that defines a 3D region. Specifically, 3D image data of type (B) is composed of, e.g. center-line coordinates and a diameter of a blood vessel. On the display device, the regions corresponding to the center-line coordinates and diameter are painted. The data mount of the 3D image data of type (B) is much smaller than the data amount of the 3D image data of type (A).
A 2D image generation unit 133 generates a pseudo-3D image (hereinafter referred to as “2D image” in order to avoid confusion with a 3D image) by, e.g. a projection process, on the basis of the 3D image data that is reconstructed by the 3D image reconstruction unit 131. The generated 2D image is displayed on the display unit 127.
Next, the operation support by the 3D image reconstruction operation supporting unit 129 is described. As is shown in
As is shown in
If the operator moves the mouse, an arrow-shaped pointer moves on the image B accordingly, along with symbol “3” that is indicative of the corresponding point 3B. When the operator moves the mouse to the same part as indicated by the characteristic point 3A, the operator clicks the mouse. Thereby, as shown in
Further when the corresponding point 3B is designated, the 3D image reconstruction operation supporting unit 129 determines whether the designated corresponding point 3B is away from an epipolar line by a predetermined distance or more. The epipolar line is defined as a line of candidate points for the corresponding point 3B that is to be designated on the image B. The epipolar line is determined by the imaging angle of the image A, the imaging angle of the image B, and the position of the point A3 on the image A. As is shown in
There occurs no geometrical contradiction even if the corresponding point 3B is present on any position on the epipolar line. The operator designates the point 3B, which anatomically corresponds to the point 3A, from over the epipolar line.
As is shown in
In a case where a corresponding point is erroneously designated, the erroneous designation of the corresponding point can be canceled and re-designation of the corresponding point is enabled in the following manner. As shown in
As shown in
If the operator desires to first designate the corresponding point 4B prior to the corresponding point 3B, the operation supporting unit 129 can operate so as to enable such designation. As is shown in
In the above example, the mark indicating the characteristic point 3A, in association with which the corresponding point 3B, for instance, is to be next designated, is displayed in a different display mode from the display mode of the other characteristic points 1A, 2A and 4A, that is, in red or in a flickering display mode. Additionally or alternatively, as shown in
The display of the epipolar line shown in
The order of designation of corresponding points is initially set to correspond to the order of designation of characteristic points. However, as shown in
As has been described above, according to the present embodiment, it is possible to reduce the load of a work of designating corresponding points, which are associated with a common part, on projection images captured in two directions, this work being needed when a 3D image is reconstructed from the projection images captured in two directions. It is also possible to provide an operation support to avoid erroneous designation of such corresponding points.
An image processing apparatus according to a second embodiment of the present invention will now be described with reference to the accompanying drawings. In this embodiment, the image processing apparatus is described as being built in a biplane X-ray imaging apparatus. Needless to say, the image processing apparatus may be constructed as a single unit. In addition, this embodiment may be constructed as a program for causing a computer to execute an image process of the image processing apparatus. A computer-readable memory medium that stores the program may also be provided.
In the description below, an object that is to be processed by the image processing apparatus of this embodiment is 3D image data (volume data) of a blood vessel, which is reconstructed from X-ray projection images that are captured substantially at the same time in two directions. However, the object to be processed by the image processing apparatus is not limited to this. The object to be processed by the image processing apparatus may be 3D image data of a blood vessel, which is reconstructed from projection images that are captured by a single-plane X-ray imaging apparatus at different times in two directions, or volume data derived from data that is acquired by other imaging apparatuses such as an X-ray computed tomography imaging apparatus (CT scanner) and a magnetic resonance imaging apparatus (MRI).
Objects for the image process are fine tubular ones that are preset in the subject, and are typically blood vessels, but the objects are not limited to blood vessels. The objects may be a catheter, a guide wire, a stent, an intravascular treatment device, a biopsy needle, forceps, an endoscope, etc.
A frame control unit 2111 arbitrarily controls the positions and directions of the C-arm 2013 and Ω-arm 2023 in accordance with the operator's instruction that is input from an operation table 2123 connected to the frame control unit 2111 via an user interface 2121, and the frame control unit 2111 acquires data relating to the imaging positions and imaging directions of the respective imaging systems from sensors (not shown). An image memory unit 2117 stores the data relating to the imaging positions and imaging directions of the respective imaging systems, together with projection image data which is generated from the X-ray detectors 2114-1 and 2114-2 via a detector control unit 2115 in sync with X-rays that are generated from the X-ray tubes 2112-1 and 2112-2 by application of tube voltage from an X-ray control unit 2113. A display unit 2127 is a display device such as a CRT, and is connected via an image display control unit 2125. A blood vessel extraction unit 2119 extracts an image of a blood vessel, which is formed by, e.g. a threshold process, from the projection image data. A 3D image reconstruction unit 2131 reconstructs 3D image data (also referred to as “volume data”) of the blood vessel that is extracted from the projection images by the blood vessel extraction unit 2119, on the basis of the positional relationship between a plurality of corresponding points which are designated by the operator and are associated with the same part between two projection images captured in two different imaging directions. A 3D image data memory unit 2132 stores 3D image data that is reconstructed by the 3D image reconstruction unit 2131.
As mentioned above, the 3D image data memory unit 2132 may be configured to store 3D image data that is generated from image data acquired by other imaging apparatuses such as an X-ray computed tomography imaging apparatus (CT scanner) and a magnetic resonance imaging apparatus (MRI). A 2D image generation unit 2133 generates a projection image as a 3D image representing a configuration of a blood vessel in a pseudo-manner (a projection image representing a blood vessel configuration) by projecting the 3D image data, which is stored in the 3D image data memory unit 2132, on a projection plane corresponding to an arbitrary view angle (imaging direction) at an arbitrary view point. The generated projection image representing the blood vessel configuration is displayed on the display unit 2127.
A blood vessel color map generation unit 2129 extracts a center axis (center line) of the blood vessel from the 3D image data stored in the 3D image data memory unit 2132, calculates a tangent vector of the blood vessel with respect to multiple points (voxels) on the center axis of the blood vessel, and calculates the angle of the tangent vector to the projection plane (angle between the tangent vector and the projection plate) with respect to each point (voxel). This angle represents the direction of running of the blood vessel. Further, the blood vessel color map generation unit 2129 converts the angle to a color value according to a pre-stored color table, and generates volume data in which the color value is set as a voxel value (hereinafter referred to as volume data relating to the direction of running of the blood vessel). The blood vessel color map generation unit 2129 projects the generated volume data relating to the direction of running of the blood vessel on the same projection plane with the same view point and the same view angle as the projection image representing the blood vessel configuration, thereby generating a color map as a projection image representing the direction of running of the blood vessel (i.e. the projection image representing the direction of running of the blood vessel). The generated color map is superimposed on the projection image representing the blood vessel configuration in an image combining unit 2135, and the resultant image is displayed on the display unit 2127.
The generation of the color map representing the direction of running of the blood vessel is described below in detail. As is shown in
In
A center axis (center line) of the blood vessel is extracted from the reconstructed volume data (S12). The method of extracting the center line of the blood vessel from the volume data may arbitrarily be chosen from conventional ones. Subsequently, as shown in
Next, as shown in
The angle is converted to a color value according to a prescribed color table as shown in
In the example of
The blood vessel color map generation unit 2129 projects the volume data, in which the color value corresponding to the angle of the blood vessel to the projection plane is set as the voxel value, on the same projection plane with the same view point and the same view angle as the projection image representing the blood vessel configuration, thereby generating a color map as a projection image representing the direction of running of the blood vessel (i.e. the projection image representing the direction of running of the blood vessel). As exemplified in
According to the present embodiment, the projection image representing the configuration of the blood vessel is colored in accordance with the angle between the direction of running of the blood vessel and the projection plane. Therefore, the direction of running of the respective parts of the blood vessel, the degree of curve of the blood vessel, etc. can exactly be recognized.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
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